1. Field of the Invention
The present invention relates to a multi-antenna module, particularly to a multi-antenna module, wherein the number of antenna units can be infinitely expanded in the same antenna structure.
2. Description of the Related Art
With the popularization of wireless communication, there are also many advances in antenna technology. Particularly, many types of Combo antenna systems have been developed to meet the tendency of miniaturizing antennae and fabricating multi-frequency communication devices, wherein different antenna structures are integrated into a single antenna module to attain a multi-frequency function and reduce the sizes of antenna systems.
Refer to FIG. 1. A Taiwanese patent No. I268010 discloses an antenna integration system for mobile phones, which comprises a baseplate 104, a planar Inverted F antenna 101, a monopole antenna 102, and a planar antenna 103. The planar Inverted F antenna 101 has a feeder point 105 and ground point 106. The monopole antenna 102 has a feeder point 107, and the planar antenna 103 has a feeder point 108. The minimum spacing between the planar Inverted F antenna 101 and the monopole antenna 102 is 6 mm. The minimum spacing between the planar Inverted F antenna 101 and the planar antenna 103 is 2 mm. In such a structure, the appropriate spacing between antennae can effectively reduce the isolation interference and enable the antennae to transmit and receive signals normally.
Referring to FIG. 2a and FIG. 2b, FIG. 2a is a diagram showing the measurement results of the isolation (S21) of the planar Inverted F antenna and the monopole antenna. FIG. 2b is a diagram showing the measurement results of the isolation (S21) of the planar Inverted F antenna and the planar antenna. From the measurement results, it is known that the antenna integration system has a better isolation than other prior arts.
To reduce the radiation interference among the antennae, the planar Inverted F antenna 101 is arranged on a first face of the baseplate 104, and the monopole antenna 102 is arranged on a lateral side of the baseplate 104, and the planar antenna 103 is arranged on the first face of the baseplate 104 but far away from the monopole antenna 102. Such a layout should increase the difficulty of installing the antenna integration system and make the antenna system hard to integrate with electronic products. The spacing between antennae has to be at least 6 mm or at least 2 mm, which greatly increases the space occupied by the system. However, the radiation efficiency of the antenna integration system is hard to obviously increase thereby. Further, the isolation effect between the antennae is likely to be constrained. In fact, the prior-art antenna integration system seldom achieves the announced function completely.